Copolycarbonates form part of the group of the technical thermoplastics. They find a variety of uses in the electrical and electronics sector, as a housing material for lights, and in applications where exceptional thermal and mechanical properties are required, for example hairdryers, applications in the automotive sector, plastic covers, headlamp lenses or light guide elements, and also lamp covers or lamp bezels. These copolycarbonates can be used as a blending partner for further thermoplastic polymers.
In the case of these compositions, it is virtually always the case that good thermal and mechanical properties such as a high Vicat temperature (heat distortion resistance) and glass transition temperature are an absolute requirement. However, high glass transition temperatures and heat distortion resistances simultaneously also lead to higher melt viscosities, which in turn has an adverse effect on processibility, for example by injection molding.
The flowability of (co)polycarbonate compositions or (co)PC blends can be increased by the addition of compounds of low molecular weight. Since substances of this kind, however, simultaneously act as plasticizers, they lower the heat distortion resistance and glass transition temperature of the polymer matrix. This again is undesirable, since this reduces the temperature use range of the materials.
DE 102004020673 describes copolycarbonates having improved flowability, based on bisphenols having an ether or thioether linkage.
DE 3918406 discloses blends for optical data storage means based on a specific polycarbonate with elastomers or other thermoplastics, and the use thereof in optical applications, specifically optical data storage means such as compact disks.
WO 03/095521 discloses a process for producing multiwall sheets by extruding a composition comprising a polycarbonate having a content of Fries structures of 10 ppm-2000 ppm.
WO 2013/045552 discloses compositions comprising a copolycarbonate based on bisphenol A and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC).
EP 0 953 605 describes linear polycarbonate compositions having improved flow characteristics, characterized in that cyclic oligocarbonates are added in large amounts, for example 0.5% to 4%, and are homogenized by means of a twin-screw extruder in the matrix of a linear BPA polycarbonate at 285° C. In this case, flowability increases with increasing amount of cyclic oligocarbonates. At the same time, however, there is a distinct decrease in glass transition temperature and hence heat distortion resistance. This is undesirable in the industrial applications of (co)polycarbonate compositions of relatively high heat distortion resistance. This disadvantage then has to be compensated for by the use of higher amounts of costly cobisphenols.
A frequent requirement in industrial applications is for high melt stiffnesses, in order to achieve adequate melt stability in the processing operation. In order to achieve this, it is necessary to incorporate branching structures into the polymer backbone in a complex manner. This inevitably leads to higher melt viscosities (see Donald G. LeGrande, John T. Bendier: “Handbook of Polycarbonate Science and Technology”, Marcel Dekker, Inc. 2000; Ludwig Bottenbruch: “Polycarbonates, Polyacetals, Polyesters, Cellulose Esters”, Hanser Verlag, 1996), which leads to disadvantages in the processing operation, since higher processing temperatures and/or higher shear rates are necessary, which lead to thermal damage to the polycarbonates.